Since a signal is transmitted through a channel having frequency selective characteristics in an indoor environment, a delayed and received symbol serves as interference with a subsequent symbol. The related art has used a code division multiple access scheme to solve inter-symbol interference (ISI), but has a problem in that a receiving apparatus is complicated. In this case, a mobile communication or Bluetooth receiving apparatus using a wireless terminal has a large volume, so that the mobile communication or Bluetooth receiving apparatus is difficult to be carried and consumes a considerable amount of power, so that the receiving apparatus is difficult to use. Therefore, in order to solve the foregoing problem, researches into a transmitting apparatus and method capable of reducing complexity of the receiving apparatus while being suitable for an indoor environment by controlling the inter-symbol interference well have been conducted.
A time reversal (TR) technique for concentrating signals on a spatial axis in a multimedia communication system in the indoor environment may minimize an interference signal transmitted to other users that are not targeted and a time reversal technique for concentrating signals on a temporal axis may reduce a delay spread of a channel to reduce the ISI. In particular, the time reversal technique for concentrating signals on the spatial axis may be very usefully used as a technique for reducing multi user interference (MUI) in a multi user environment. However, although a transmitting signal to noise ratio is very high, the time reversal technique cannot completely remove the MUI occurring on the spatial axis and the ISI occurring on the temporal axis, thereby causing performance degradation.
A zero-forcing (ZF) technique sets the inter-symbol interference to be 0, so that when a signal to noise ratio is very high, performance is greatly improved. However, since the zero-forcing technique is a filter for the purpose of reducing interference, a magnitude in a main peak of a received signal becomes relatively very small. Therefore, when the ZF technique is exposed to actually used environmental noises, performance may be degraded.
A technique proposed to overcome the disadvantage of the ZF technique and the disadvantage of the time reversal technique is a joint ZF-TR technique.
The joint ZF-TR technique is a filter that sets the interference to be 0 and maximizes the signal to noise ratio. However, referring to solutions actually obtained by the joint ZF-TR technique, the joint ZF-TR technique shows a main peak value higher than that of the ZF technique, but shows a main peak value lower than that of the TR technique that maximizes the signal to noise ratio. Therefore, the performance may be degraded under the situation in which the environment is poor.